The present invention concerns a portable electronic device including a wristband, a case and an electronic circuit for receiving radiobroadcast signals comprising an antenna disposed in said wristband.
More precisely, the present invention concerns a particular antenna structure that allows the portable device to receive signals whose frequency is located in the very high frequency range, i.e. VHF waves, with a high level of sensitivity. Preferably, said antenna is capable of receiving signals belonging to the FM (“frequency modulation”) band frequency range, in other words whose frequency is substantially comprised between 87 and 110 MHz.
Such devices have already been disclosed in the prior art and in particular, very varied antenna structures have been proposed.
One may, for example, refer to U.S. Pat. No. 4,754,285, granted 28 Jun. 1988, which discloses a wristwatch incorporating in particular a circuit for receiving radiobroadcast signals requiring the use of an antenna. The solution disclosed consists in arranging a metal wire in an extensible wristband across its entire length and such that said wire goes successively around in the direction of the width of said wristband. Thus, the length of the wire is greater than the length of said wristband in the rest position, which then allows the wristband to be extended.
However, this solution, in addition to taking up a significant amount of space in the wristband, is not suitable for watches whose wristband comprises two strands closing over each other via a fastening device.
Other solutions have been presented to respond to this particular case, such as a simple metal wire loop passing through each of the two strands of the wristband from the end connected to the watchcase to the end carrying the means for fastening it to the other strand. Means are also provided for establishing an electric connection between the two parts of the loop at the location of the fastening means.
However, these connection means complicate the construction of the wristband, all the more so since they are preferably protected from the external environment, in particular from the perspiration of the person wearing the watch, which means significant protective measures have to be taken.